Low-temperature melting permeation continuous separation method for aluminum industry carbon-based hazardous wastes, and product obtained through the method

Abstract

The invention provides a low-temperature melting permeation continuous separation method for aluminum industry carbon-based hazardous wastes, and a product obtained through the method. The method includes the steps of: S1) performing crushing and iron removal pretreatment to the aluminum industry carbon-based hazardous wastes; S2) after the pretreatment, performing low-temperature electric calcination to the hazardous wastes at 1050-1200 DEG C so that fluoride salts are molten and are separated through permeation; S3) performing permeation impurity removal to the remained low-fluorine carbon granules, and feeding the carbon granules into a high-temperature electric calcination furnace to perform high-temperature electric calcination, thereby producing high-purity carbon products. The invention also provides a low-temperature melting permeation continuous separation system for the aluminum industry carbon-based hazardous wastes. By means of the method, harmless treatment and recycling utilization of three hazardous wastes, including fluoride salt containing anode scraps, anode carbon residues and wasted cathodes, in aluminum industry can be carried out with low cost and high efficiency. A fluoride salt product recovered through the continuous low-temperature melting permeation impurity removal and separation method is high in whiteness and purity, wherein all performance indices are higher than that of second-stage products in national standard.

Description

technical field [0001] The invention belongs to the technical field of solid waste treatment, and in particular relates to a method and system for harmless treatment and resource utilization of aluminum electrolysis fluorine-containing carbon solid waste. Background technique [0002] The anode remnants and spent cathodes containing fluoride salts in the aluminum industry contain about 30% fluoride salts, and the anode carbon residues contain about 70% fluoride salts. In addition, they also contain 0.01% to 0.1% sodium cyanide, which is a dangerous solid. Waste, if not disposed of properly, will bring serious pollution to the environment, air, soil or groundwater, and directly endanger human health; in addition, these three hazardous solid wastes contain a small amount of aluminum nitride and a small amount of iron, aluminum, calcium, Except for magnesium oxide or aluminosilicate impurities, the rest are fluoride salts and carbon, which have high resource utilization value. ...

AI Technical Summary

Problems solved by technology

The advantage of this method is that there is no secondary carbon hazardous solid waste; the disadvantage is that the obtained fluoride salt electrolyte coexists with impurities, and its purity and whiteness are not high, so it cannot be directly reused in the electrolytic aluminum production process; in addition, burning carbon , except that there is a large amount of CO 2 In addition to the problem of emptying, there are also a certain amount of CO and NO x And gaseous fluoride salt or fluoride salt solid particles and other harmful substances are emptied, the harmless disposal and resource utilization are not in place, and it is contrary to the national policy of energy saving, emission reduction and environmental protection;

[0005] 3. Disposal of anode carbon slag by smelting: put the anode carbon slag in a container for heating and smelting, the fluoride salt and impurities are melted and left in the lower part of the container, the carbon floats to the top of the fluoride salt and impurity molten liquid, and the carbon is removed. Then pour out or discharge the fluoride salt and impurity molten liquid, cool and collect; this method has two shortcomings: one is that the collected fluoride salt and impurities coexist, the whiteness and purity are not high, and it cannot be returned directly The aluminum electrolysis production process is used; the second is that the extracted charcoal still contains about 15% fluoride salt, and the resulting charcoal is still a hazardous solid waste;

[0006] 4. Grinding-water immersion-flotation- filtrate evaporative crystallization, or acid leaching to dispose of electrolytic aluminum waste cathode. The advantage of this method is that the purity of sodium fluoride obtained by water leaching filtrate evaporative crystallization process is relatively high; the disadvantage is that the fluoride in the spent cathode Aluminum and cryolite cannot be leached and recovered, and coexist with carbon, and sodium fluoride is also incompletely leached, and carbon products are still hazardous solid waste. In addition, the evaporation and crystallization system requires large investment and energy consumption;

This method still has the problem that the process is difficult to realize. For example, when the mist water sprays and adsorbs the fluorine vapor in the waste gas (the temperature of the fluorine vapor is extremely high), a large amount of water vapor will be generated, and the water vapor will carry a higher concentration of fluorine vapor. For fluoride salt and HF gas, the tail gas installed on the top of the water mist spray device is difficult to discharge qualifiedly; the temperature gradient from the atomization spray device to the exhaust gas outlet of the high temperature furnace is 110 ° C ~ the temperature required by gaseous fluoride salt, this temperature gradient Under the condition, the channel is easy to generate thick liquid and condense into solid, causing the channel to be blocked

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